error while converting complex models to onnx model (caused by view_as_complex)

🐛 Bug

While exporting to onnx some of the models (with complex operation). There is error caused by no support of complex casting in the onnx ops set torch.view_as_complex(input))

To Reproduce

torch.onnx.export(model_dccrn, input_random, 'model_dccrn.onnx', verbose=True,  opset_version=11)

Steps to reproduce the behavior (code sample and stack trace):

~/lib/miniconda3/lib/python3.9/site-packages/torch/onnx/symbolic_registry.py in get_registered_op(opname, domain, version)
    114         else:
    115             msg += "Please feel free to request support or submit a pull request on PyTorch GitHub."
--> 116         raise RuntimeError(msg)
    117     return _registry[(domain, version)][opname]

RuntimeError: Exporting the operator view_as_complex to ONNX opset version 12 is not supported. Please feel free to request support or submit a pull request on PyTorch GitHub.

Expected behavior

The convertion should proceed without errors and end with proper onnx model.

Environment

Package versions

Run asteroid-versions and paste the output here:

Asteroid            0.5.1
PyTorch             1.9.0
PyTorch-Lightning   1.3.8

Additional info

I know it is not set case in pytorch-onnx ops set

ONNX current operations:

• https://github.com/onnx/onnx/blob/master/docs/Operators.md
  • in part for Cast

  • Casting to complex is not supported.

issues with errors:

• error with support view_as_complex for converting to onnx model
  • view_as_complex https://pytorch.org/docs/stable/generated/torch.view_as_complex.html
  • https://github.com/onnx/onnx/issues/3173
  • https://github.com/pytorch/pytorch/issues/49793

However, we can propose a wrapper that is covering this convertion in such a way that onnx model will be created properly.

view_as_complex is implemented in ATen library

• https://github.com/pytorch/pytorch/blob/30e48bbeae545c3292c2ab3fed0cb2dba4a92fed/aten/src/ATen/native/ComplexHelper.h#L70 const auto new_strides = computeStrideForViewAsComplex(self.strides()); const auto complex_type = c10::toComplexType(self.scalar_type()); view_tensor(self, complex_type, new_storage_offset, new_sizes, new_strides);

[mpariente]

I guess for simple operations, it’s possible, but when solve and eigenvalue decompositions are computed, having the facade is more complicated, right?

I don’t really know what we should do about that.

[cyrta]

Thanks a lot, I am debugging some of the models with asteroid complex representation and there are still some errors. I think all of the error places are in complex_nn.